Add constant values for MPEG-H.

MPEG-H is a new surround audio codec. Low complexity and baseline with
audio level as 3 and 4 is defined since they are relevant for the
current and upcoming commercial services.

Bug: 178619392
Test: make, atest AudioFormatTest
Change-Id: Iea5432765abeb485a31c8848793dffce1d4c6a0b